1. Field of Invention
This disclosure relates to earth boring reamer bits, and particularly to reamer bits having a balanced cutting structure.
2. Description of Prior Art
Drill bits used in drilling of subterranean well bores typically comprise fixed cutter bits and roller cone bits. Roller cone bits typically comprise a body having legs extending downward and a head bearing extending from the leg towards the axis of the bit body. Frustoconically shaped roller cones are rotatably mounted on each of these journals and are included with cutting teeth on the outer surface of these cones. As the bit rotates, the cones rotate to cause the cutting elements to disintegrate the earth formation.
In some situations a pilot reamer drilling system is employed where two or more bits are combined on a single drill string. Here the lowermost bit, commonly referred to as a pilot bit, creates a pilot hole and an upper earth boring bit enlarges the pilot hole diameter. The bit enlarging the hole diameter is referred to as a reamer. Typically the pilot bit comprises a conventional bit, i.e. either a roller cone bit or a fixed cutter bit. The reamer bit usually employs rolling cutters as cutting members that are attached to the reamer body. Pilot reamer drilling systems are used to drill large diameter boreholes that require enhanced stabilization.